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Abstract:

A therapy delivery component is connected to an IMD with a coupling that
has a known physical property, based upon which the type and/or
connection status of the therapy delivery component is automatically
identified.

Claims:

1. A system comprising: an implantable medical device (IMD); a therapy
delivery component configured to deliver therapy to a patient; a coupling
connecting the therapy delivery component to the IMD; and a measurement
circuit configured to apply an electrical input across the coupling and
identify the therapy delivery component based on an electrical signal
generated as an output upon application of the input across the coupling.

2. The system of claim 1, wherein the coupling comprises: a first
connector connected to an end of the therapy delivery component, wherein
the first connector has an electrical resistance; and a second connector
connected to the IMD and the measurement circuit and configured to
receive the first connector.

3. The system of claim 2, wherein the measurement circuit is configured
to apply the electrical input to the second connector and the electrical
signal generated as an output upon application of the input across the
coupling comprises a voltage generated when the first connector is
connected to the second connector, and wherein the measurement circuit
identifies the therapy delivery component based on the voltage.

4. The system of claim 3, wherein the measurement circuit identifies the
therapy delivery component by calculating the resistance of the first
connector from the voltage.

5. The system of claim 1, wherein the coupling comprises: a first
connector connected to an end of the therapy delivery component; a second
connector connected to the IMD and the measurement circuit and configured
to receive the first connector; and a dielectric interposed between the
first and the second connectors.

6. The system of claim 5, wherein the measurement circuit is configured
to apply the electrical input to the second connector and the electrical
signal generated as an output upon application of the input across the
coupling comprises a voltage generated when the first connector is
connected to the second connector, and wherein the measurement circuit
identifies the therapy delivery component based on the voltage.

7. The system of claim 1, wherein the processor is configured to
determine compatibility of the therapy delivery component with a Magnetic
Resonance Imaging (MRI) system.

8. The system of claim 1, wherein the therapy delivery component
comprises at least one of a catheter or an electrical stimulation lead.

9. The system of claim 1, wherein the electrical input comprises at least
one of a constant current or a constant voltage input.

10. A method comprising: applying an electrical input across a coupling
between an implantable medical device (IMD) and a therapy delivery
component configured to deliver therapy to a patient; generating an
electrical signal as an output to the electrical input applied across the
coupling; and identifying the therapy delivery component based on the
electrical signal.

11. The method of claim 10, wherein the coupling comprises: a first
connector connected to an end of the therapy delivery component and
comprising a resistance; and a second connector connected to the IMD and
configured to receive the first connector.

12. The method of claim 11, wherein generating the output electrical
signal comprises generating a voltage signal when the first connector is
connected to the second connector as an output to an input current
applied across the first connector, and wherein identifying the therapy
delivery component comprises identifying the therapy delivery component
based on the voltage.

13. The method of claim 10, wherein the coupling comprises: a first
connector connected to an end of the therapy delivery component; a second
connector connected to the IMD and configured to receive the first
connector; and a dielectric interposed between the first and the second
connectors.

14. The method of claim 13, wherein generating the output electrical
signal comprises generating a voltage signal when the first connector is
connected to the second connector as an output to an input current
applied across the first connector, and wherein identifying the therapy
delivery component comprises identifying the therapy delivery component
based on the voltage.

15. The method of claim 10 further comprising determining compatibility
of the therapy delivery component with a Magnetic Resonance Imaging (MRI)
system based on the electrical signal generated as an output to the
electrical input applied across the coupling.

16. The method of claim 10, wherein the therapy delivery component
comprises at least one of a catheter or a medical lead.

17. A system comprising: means for applying an electrical input across a
coupling between an implantable medical device (IMD) and a therapy
delivery component configured to deliver therapy to a patient; means for
generating an electrical signal as an output to the electrical input
applied across the coupling between an implantable medical device (IMD)
and a therapy delivery component configured to deliver therapy to tissue
of a patient; and means for identifying the therapy delivery component
based on the electrical signal.

18. A system comprising: an implantable medical device (IMD); a therapy
delivery component configured to deliver therapy to a patient; a coupling
connecting the therapy delivery component to the IMD; and a measurement
circuit configured to apply an electrical input across the coupling and
identify a connection status between the IMD and the therapy delivery
component based on an electrical signal generated as an output upon
application of the input across the coupling.

19. The system of claim 18, wherein the connection status between the IMD
and the therapy delivery component comprises at least one of connected,
disconnected, or partially disconnected.

20. The system of claim 19 further comprising a processor connected to
the measurement circuit, and wherein the processor is configured to
receive the connection status from the measurement circuit and generate
an alert when the connection status between the IMD and the therapy
delivery component comprises at least one of disconnected or partially
disconnected.

21. The system of claim 20, wherein the alert comprises at least one of
an audible, tactile, or visual alert.

22. The system of claim 20 further comprising a programmer
communicatively connected to the IMD, wherein the programmer comprises
the processor.

23. A method comprising: applying an electrical input across a coupling
between an implantable medical device (IMD) and a therapy delivery
component configured to deliver therapy to a patient; generating an
electrical signal as an output to the electrical input applied across the
coupling; and identifying a connection status between the IMD and the
therapy delivery component based on the electrical signal.

24. The method of claim 23, wherein the connection status between the IMD
and the therapy delivery component comprises at least one of connected,
disconnected, or partially disconnected.

25. The method of claim 23 further comprising generating an alert when
the connection status between the IMD and the therapy delivery component
comprises at least one of disconnected or partially disconnected.

26. The method of claim 25, wherein the alert comprises at least one of
an audible, tactile, or visual alert.

27. A system comprising: means for applying an electrical input across a
coupling between an implantable medical device (IMD) and a therapy
delivery component configured to deliver therapy to a patient; means for
generating an electrical signal as an output to the electrical input
applied across the coupling between an implantable medical device (IMD)
and a therapy delivery component configured to deliver therapy to tissue
of a patient; and means for identifying a connection status between the
IMD and the therapy delivery component based on the electrical signal.

Description:

TECHNICAL FIELD

[0001] This disclosure relates to implantable medical devices.

BACKGROUND

[0002] A variety of medical devices are used for chronic, i.e., long-term,
delivery of fluid therapy to patients suffering from a variety of
conditions, such as chronic pain, tremor, Parkinson's disease, epilepsy,
urinary or fecal incontinence, sexual dysfunction, obesity, spasticity,
or gastroparesis. For example, pumps or other fluid delivery devices can
be used for chronic delivery of therapeutic fluids, such as drugs to
patients. These devices are intended to provide a patient with a
therapeutic output to alleviate or assist with a variety of conditions.
Typically, such devices are implanted in a patient and provide a
therapeutic output under specified conditions on a recurring basis.

[0003] One type of implantable fluid delivery device is a drug infusion
device that can deliver a drug or other therapeutic fluid to a patient at
a selected site. A drug infusion device may be partially or completely
implanted at a location in the body of a patient and deliver a fluid
medication through a catheter to a selected delivery site in the body.
Drug infusion devices, such as implantable drug pumps, commonly include a
reservoir for holding a supply of the therapeutic fluid, such as a drug,
for delivery to a site in the patient. The fluid reservoir can be
self-sealing and accessible through one or more ports. A pump is fluidly
coupled to the reservoir for delivering the therapeutic fluid to the
patient. A catheter provides a pathway for delivering the therapeutic
fluid from the pump to a delivery site in the patient.

SUMMARY

[0004] In general, this disclosure describes techniques for automatically
identifying the type and/or connection status of a therapy delivery
component connected to an implantable medical device (IMD). In one
example, a system includes an IMD, a therapy delivery component, a
coupling, and a measurement circuit. The therapy delivery component is
configured to deliver therapy to a patient. The coupling connects the
therapy delivery component to a housing of the IMD. The measurement
circuit is configured to apply an electrical input across the coupling
and identify the therapy delivery component based on an electrical signal
generated as an output upon application of the input across the coupling.

[0005] In another example, a method includes applying an electrical input
across a coupling between an implantable medical device (IMD) and a
therapy delivery component configured to deliver therapy to a patient,
generating an electrical signal as an output to the electrical input
applied across the coupling, and identifying the therapy delivery
component based on the electrical signal.

[0006] In another example, a system includes means for applying an
electrical input across a coupling between an implantable medical device
(IMD) and a therapy delivery component configured to deliver therapy to a
patient, means for generating an electrical signal as an output to the
electrical input applied across the coupling between an implantable
medical device (IMD) and a therapy delivery component configured to
deliver therapy to tissue of a patient, and means for identifying the
therapy delivery component based on the electrical signal.

[0007] In another example, a system includes an IMD, a therapy delivery
component, a coupling, and a measurement circuit. The therapy delivery
component is configured to deliver therapy to a patient. The coupling
connects the therapy delivery component to the IMD. The measurement
circuit is configured to apply an electrical input across the coupling
and identify a connection status between the IMD and the therapy delivery
component based on an electrical signal generated as an output upon
application of the input across the coupling.

[0008] In another example, a method includes applying an electrical input
across a coupling between an implantable medical device (IMD) and a
therapy delivery component configured to deliver therapy to a patient.
generating an electrical signal as an output to the electrical input
applied across the coupling, and identifying a connection status between
the IMD and the therapy delivery component based on the electrical
signal.

[0009] In another example, a system includes means for applying an
electrical input across a coupling between an implantable medical device
(IMD) and a therapy delivery component configured to deliver therapy to a
patient, means for generating an electrical signal as an output to the
electrical input applied across the coupling between an implantable
medical device (IMD) and a therapy delivery component configured to
deliver therapy to tissue of a patient, and means for identifying a
connection status between the IMD and the therapy delivery component
based on the electrical signal.

[0010] The details of one or more examples disclosed herein are set forth
in the accompanying drawings and the description below. Other features,
objects, and advantages will be apparent from the description and
drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0011]FIG. 1 is a conceptual diagram illustrating an example of a fluid
delivery system including an implantable fluid delivery device configured
to deliver a therapeutic fluid to a patient via a catheter.

[0012]FIG. 2 is functional block diagram illustrating an example of the
implantable fluid delivery device and catheter of FIG. 1.

[0013]FIG. 3 is a plan view of an example configuration of an implantable
fluid delivery device.

[0014] FIGS. 4A-4C are examples of measurement circuits that may be
included in the implantable fluid delivery device of FIG. 3.

[0015]FIG. 5 is a functional block diagram illustrating an example of an
external programmer shown in FIG. 1.

[0016]FIG. 6 is a flow chart illustrating an example method of
identifying a therapy delivery component.

[0018]FIG. 8 is a conceptual diagram illustrating an example
configuration of the implantable pulse generator and lead of FIG. 7.

DETAILED DESCRIPTION

[0019] IMDs, including, e.g. therapeutic fluid delivery devices and
electrical stimulation devices, commonly include the actual implantable
device, including, e.g., a housing containing a battery, device
circuitry, in the case of fluid delivery devices, a therapeutic fluid
reservoir and a pumping mechanism, in the case of stimulation devices, a
pulse generator, and a therapy delivery component, e.g. a catheter and/or
a stimulation lead to deliver therapy to a point of interest within a
patient. In some examples, both the IMD and the therapy delivery
component are implanted and the IMD, e.g. a processor of the device is
programmed to deliver the appropriate therapy to a patient via the
delivery component.

[0020] Following implantation during initial and subsequent programming
sessions, a user, e.g., a clinician, is required to select the correct
therapy delivery component prior to programming the therapy. A therapy
delivery component may be, for example, a catheter or electrical lead.
For example, the user may be required to select the correct model number
and configuration of the catheter or lead implanted within the patient
prior to programming the therapy. Selecting the type of therapy delivery
component actually implanted is an important step in delivering effective
therapy to the patient. However, dependency on user selection makes the
process susceptible to human error. The selection process can also be
time consuming. For example, where the therapy delivery component
information is not available, the clinician may have to follow a number
of time consuming steps to obtain the information, including, e.g.
calling technical services or taking a fluoroscopic image (for compatible
therapy delivery components). In view of the foregoing manual, time
consuming, and error prone processes, this disclosure describes
techniques for automatically identifying the type of therapy delivery
component connected to an IMD.

[0021]FIG. 1 is a conceptual diagram illustrating an example of a therapy
system 10, which includes IMD 12, a therapy delivery component, which, in
the example of FIG. 1 is catheter 18, and external programmer 20. IMD 12
is connected to catheter 18 to deliver at least one therapeutic fluid,
e.g. a pharmaceutical agent, pain relieving agent, anti-inflammatory
agent, gene therapy agent, or the like, to a target site within patient
16. IMD 12 includes an outer housing that, in some examples, is
constructed of a biocompatible material that resists corrosion and
degradation from bodily fluids including, e.g., titanium or biologically
inert polymers. IMD 12 may be implanted within a subcutaneous pocket
relatively close to the therapy delivery site. For example, in the
example shown in FIG. 1, IMD 12 is implanted within an abdomen of patient
16. In other examples, IMD 12 may be implanted within other suitable
sites within patient 16, which may depend, for example, on the target
site within patient 16 for the delivery of the therapeutic fluid. In
still other examples, IMD 12 may be external to patient 16 with a
percutaneous catheter connected between IMD 12 and the target delivery
site within patient 16.

[0023] Catheter 18 can comprise a unitary catheter or a plurality of
catheter segments connected together to form an overall catheter length.
External programmer 20 is configured to wirelessly communicate with IMD
12 as needed, such as to provide or retrieve therapy information or
control aspects of therapy delivery (e.g., modify the therapy parameters
such as rate or timing of delivery, turn IMD 12 on or off, and so forth)
from IMD 12 to patient 16.

[0024] Catheter 18 may be coupled to IMD 12 either directly or with the
aid of a catheter extension (not shown in FIG. 1). In the example shown
in FIG. 1, catheter 18 traverses from the implant site of IMD 12 to one
or more targets proximate to spinal cord 14. Catheter 18 is positioned
such that one or more fluid delivery outlets (not shown in FIG. 1) of
catheter 18 are proximate to the targets within patient 16. In the
example of FIG. 1, IMD 12 delivers a therapeutic fluid through catheter
18 to targets proximate to spinal cord 14.

[0025] IMD 12 can be configured for intrathecal drug delivery into the
intrathecal space, as well as epidural delivery into the epidural space,
both of which surround spinal cord 14. In some examples, multiple
catheters may be coupled to IMD 12 to target the same or different nerve
or other tissue sites within patient 16, or catheter 18 may include
multiple lumens to deliver multiple therapeutic fluids to the patient.
Therefore, although the target site shown in FIG. 1 is proximate to
spinal cord 14 of patient 16, other applications of therapy system 10
include alternative target delivery sites in addition to or in lieu of
the spinal cord of the patient.

[0026] Programmer 20 is an external computing device that is configured to
communicate with IMD 12 by wireless telemetry. For example, programmer 20
may be a clinician programmer that the clinician uses to communicate with
IMD 12 and program therapy delivered by the IMD. Alternatively,
programmer 20 may be a patient programmer that allows patient 16 to view
and modify therapy parameters associated with therapy programs. The
clinician programmer may include additional or alternative programming
features than the patient programmer. For example, more complex or
sensitive tasks may only be allowed by the clinician programmer to
prevent patient 16 from making undesired or unsafe changes to the
operation of IMD 12. Programmer 20 may be a handheld or other dedicated
computing device, or a larger workstation or a separate application
within another multi-function device.

[0027] As described in greater detail below, in examples according to this
disclosure, a therapy delivery component is connected to an IMD with a
coupling that has a known physical property, e.g. electrical resistance
or capacitance, based upon which the type and particular configuration of
the therapy delivery component may be identified. For example, the
therapy delivery component of system 10 of FIG. 1, i.e. catheter 18 may
be connected to IMD 12 with a coupling that has a known electrical
resistance. In one example, connecting the catheter to the IMD with the
coupling closes a circuit that may apply an electrical input, e.g., a
predetermined measurement current across the coupling. The type and
particular configuration of catheter 18 may, in turn, be identified based
on a signal generated as an output in response to the input applied
across the coupling between the catheter and IMD 12. For example, the
type and configuration of catheter 18 may be identified based on a
voltage signal generated as an output to the current input applied across
the coupling with the known resistance. The voltage signal generally will
be linearly proportional to the resistance.

[0028] As used in this disclosure, coupling refers to a structure or a
number of structures that connect an IMD and a therapy delivery
component. The term coupling, alone, does not denote any specific
structure for achieving the function of connecting the IMD to the therapy
delivery component. As such, other terms could be used to describe a
coupling within the meaning of this disclosure, including, e.g.
connection, connector, junction, joint, fastener, clasp and link.

[0029] In one example, the coupling between catheter 18 and IMD 12 in the
example of FIG. 1 may include a first connector connected to proximal end
18A of the catheter. Some part or all of the first connector connected to
end 18A of catheter 18 may include, e.g., a known electrical resistance.
The coupling may also include a second connector connected to IMD 12 and
measurement circuit included in the IMD. The second connector is
configured to receive the connector connected to end 18A of catheter 18.
In such an example, connecting the first connector connected to end 18A
of catheter 18 with the second connector connected to IMD 12 may close a
circuit between the coupling and the measurement circuit of the IMD 12.
The measurement circuit may apply an electrical input across the
coupling, the application of which generates a voltage signal as an
output. The measurement circuit of IMD 12 may then identify the type of
therapy delivery component based on the voltage.

[0030] For example, the measurement circuit may measure the voltage output
signal and transmit the signal to a processor of IMD 12, e.g., via an
analog-to-digital converter (ADC), which converts the signal to a digital
value. The processor then may identify the time of circuit based on the
digital value, e.g., by comparing the digital value to one or more
digital threshold values. The processor of IMD 12 may then
cross-reference the voltage value in a look-up table or other organized
aggregation of data of therapy delivery components and associated
voltages stored on memory of the IMD or another device, e.g. programmer
20. In another example, the measurement circuit may identify the type and
configuration of catheter 18 by calculating the resistance of the first
connector from the voltage. For example, the measurement circuit may
measure the voltage output signal and transmit the value to a processor
of IMD 12, which processor may, in turn, calculate the resistance of the
first connector from the voltage generated by the coupling between the
IMD and catheter 18 and search for the resistance in a look-up table or
other organized aggregation of data of therapy delivery components and
associated resistances stored on memory of the IMD or another device,
e.g. programmer 20. As a further alternative, in some examples, an analog
comparator or other circuit associated with the measurement circuit may
compare the signal to threshold voltage to generate an indication of the
type of catheter, and communicate the signal to the processor, e.g., via
an ADC.

[0031] In other examples, the first connector of the coupling between
catheter 18 and IMD 12 may include a known capacitance instead of
resistance, by which, in a similar fashion as described in the foregoing
example, the type and particular configuration of the catheter connected
to the IMD may be identified. Additional configurations of the coupling
between a therapy delivery component and an IMD are described below with
reference to FIG. 3.

[0033] IMD 12 also includes power source 44, which is configured to
deliver operating power to various components of the IMD. In some
examples, IMD 12 may include a number of reservoirs for storing more than
one type of therapeutic fluid. In some examples, IMD 12 may include a
single long tube that contains the therapeutic fluid in place of a
reservoir. However, for ease of description, an IMD 12 including a single
reservoir 34 is primarily described with reference to the disclosed
examples.

[0034] During operation of IMD 12, processor 26 controls fluid delivery
pump 32 with the aid of instructions associated with program information
that is stored in memory 28 to deliver a therapeutic fluid to patient 16
via catheter 18. Instructions executed by processor 26 may, for example,
define therapy programs that specify the dose of therapeutic fluid that
is delivered to a target tissue site within patient 16 from reservoir 30
via catheter 18. The programs may further specify a schedule of different
therapeutic fluid rates and/or other parameters by which IMD 12 delivers
therapy to patient 16.

[0035] In general, a therapy program stored on memory 28 and executed by
processor 26 defines one or more therapeutic fluid doses to be delivered
from reservoir 34 to patient 16 through catheter 18 by IMD 12. A dose of
therapeutic fluid generally refers to a total amount of therapeutic
fluid, e.g., measured in milligrams or other volumetric units, delivered
over a total amount of time, e.g., per day or twenty-four hour period.
The amount of therapeutic fluid in a dose may convey to a caregiver an
indication of the probable efficacy of the fluid and the possibility of
side effects.

[0036] In general, a sufficient amount of the fluid should be administered
in order to have a desired therapeutic effect, such as pain relief.
However, the amount of the therapeutic fluid delivered to the patient
should be limited to a maximum amount, such as a maximum daily amount, in
order not to avoid potential side effects. Therapy program parameters
specified by a user, e.g., via programmer 20 may include fluid volume per
dose, dose time period, maximum dose for a given time interval e.g.,
daily. In some examples, dosage may also prescribe particular
concentrations of active ingredients in the therapeutic fluid delivered
by IMD 12 to patient 16.

[0037] The manner in which a dose of therapeutic fluid is delivered to
patient 16 by IMD 12 may also be defined in the therapy program. For
example, processor 26 of IMD 12 may be programmed to deliver a dose of
therapeutic fluid according to a schedule that defines different rates at
which the fluid is to be delivered at different times during the dose
period, e.g. a twenty-four hour period. The therapeutic fluid rate refers
to the amount, e.g. in volume, of therapeutic fluid delivered over a unit
period of time, which may change over the course of the day as IMD 12
delivers the dose of fluid to patient 16.

[0038] As an example, IMD 12 could be programmed to deliver therapeutic
fluid to patient 16 at a rate of 20 microliters per hour. In the event
the therapy program prescribes this fluid delivery rate for a twenty four
hour period and assuming no patient or other boluses during the period of
time, the dose of fluid delivered to patient 16 by IMD 12 will be 480
microliters (per twenty four hours). The therapy program may include
other parameters, including, e.g., definitions of priming and patient
boluses, as well as time intervals between successive patient boluses,
sometimes referred to as lock-out intervals.

[0039] Therapy programs may be a part of a program group, where the group
includes a number of therapy programs. Memory 28 of IMD 12 may store one
or more therapy programs, as well as instructions defining the extent to
which patient 16 may adjust therapy parameters, switch between therapy
programs, or undertake other therapy adjustments. Patient 16 or a
clinician may select and/or generate additional therapy programs for use
by IMD 12, e.g., via external programmer 20 at any time during therapy or
as designated by the clinician.

[0040] Components described as processors within IMD 12, external
programmer 20, or any other device described in this disclosure may each
include one or more processors, such as one or more microprocessors,
digital signal processors (DSPs), application specific integrated
circuits (ASICs), field programmable gate arrays (FPGAs), programmable
logic circuitry, or the like, either alone or in any suitable
combination.

[0041] In one example, processor 26 of IMD 12 is programmed to deliver a
dose of therapeutic fluid to patient 16, which is defined in memory 28 of
the device by a volume of therapeutic fluid delivered to the patient in
one day. IMD 12 may also be programmed according to a therapy schedule
such that the fluid is delivered at different rates at different times
during the day, which may be stored in the device memory, e.g., as a
look-up table associating different fluid rates at different times during
the day.

[0042] Regardless of the particular manner in which IMD 12 is programmed
to deliver a therapeutic fluid to patient 16, an important operational
parameter of the IMD is the size and configuration of the therapy
delivery component connected to the IMD, i.e. catheter 18 in the examples
of FIGS. 1 and 2. For example, in order to program IMD 12, e.g. during a
clinician guided programming session using, e.g., programmer 20, the
clinician may need to identify catheter 18. For example, the size and
configuration of catheter 18 may affect the rate, frequency, and volume
of fluid delivered to patient 16.

[0043] Additionally, the size of catheter 18, e.g., the diameter of the
lumen of the catheter may need to be known in order to properly calculate
priming, bridge, supplemental, or other boluses. A priming bolus refers
to a bolus delivered by IMD 12 to move the fluid to the distal tip 18B of
catheter 18. A bridging bolus, which can also be referred to as a bridge
is performed when a new fluid is inserted into a reservoir of IMD 12
while an old fluid is still present in the device, e.g., within internal
tubing of the device and/or within catheter 18 connected to the device.
The bridge is performed to define a rate at which to deliver the old
fluid until the old fluid is completely delivered out of catheter 18 and
to patient 16 such that IMD 12 contains only the new fluid. A
supplemental bolus is a bolus administered to patient 16 outside of a
programmed therapy schedule. The terms patient, independent, one-time,
and therapeutic bolus may also be used in this disclosure to refer to a
supplemental bolus. Errors in bolus definitions can lead to improper
dosing of patient 16.

[0044] In the past, clinicians have commonly identified therapy delivery
components connected to an IMD by manually selecting the type and
configuration of the catheter from an array of possible types and
configurations. However, manual identification is susceptible to human
error, which may result in improperly identifying the therapy delivery
component connected to the IMD, e.g. catheter 18 connected to IMD 12. As
such, in examples according to this disclosure, a therapy delivery
component is connected to an IMD with a coupling that is configured to
generate a signal based upon which the type and particular configuration
of the therapy delivery component may be identified.

[0045] Measurement circuit 50, alone or in conjunction with other
components, including, e.g., processor 26 of IMD 12 or a processor of
programmer 20 or another device communicatively connected to IMD 12, may
be configured to identify catheter 18 based on a signal generated as an
output sensed in response to an electrical input applied across coupling
42 between the catheter and IMD 12. For example, the type and particular
configuration of catheter 18 may be identified by processor 26 based on a
signal generated as an output to an electrical input applied by
measurement circuit 50 across coupling 42 when the catheter and IMD 12
are connected by the coupling. Upon identification of catheter 18, in one
example, processor 26 may control telemetry module 30 to communicate the
type and configuration of the therapy delivery component to programmer
20, e.g., for use by a clinician in programming IMD 12 to deliver therapy
to patient 16. In addition to or in lieu of transmitting the type and
configuration of catheter 18 to programmer 20, or another device
communicatively connected to IMD 12, the IMD, and, in particular, e.g.,
processor 26 may store the information about the therapy delivery
component on memory 28, and/or on memory of another device, e.g.
programmer 20. An example configuration of IMD 12 including coupling 42
is illustrated in FIG. 3. Additionally, examples of measurement circuit
50 are illustrated in FIGS. 4A-4C.

[0046]FIG. 3 is a plan view of an example configuration of IMD 12
including catheter 18, fluid delivery pump 32, refill port 36, CAP 40,
and CAP septum 100. IMD 12 includes housing 102 and header 104, which
includes CAP 40 and CAP septum 100. In another example, however, CAP 40
and septum 100 may be arranged in another location in housing 102 of IMD
12. As described above, fluid delivery pump 32 is connected to CAP 40 by
internal tubing 38 (not shown in FIG. 3). Fluid delivery pump 32 is also
connected to catheter extension 106 via tubing 38 in header 104. Internal
tubing 38 may be a segment of tubing or a series of cavities within IMD
12 that run from reservoir 34, around or through fluid delivery pump 32
to catheter access port 40. Catheter extension 106 is connected to
proximal end 18A of catheter 18, from which the catheter extends from IMD
12 to the target delivery site within patient 16. In other examples, IMD
12 may not include catheter extension 106, in which case, catheter 18
may, e.g., be directly connected to tubing 38 in header 104 of the IMD.

[0047] Catheter 18 is connected to IMD 12 by coupling 42. In the example
of FIG. 3, coupling 42 is incorporated into the connection between
catheter 18 and extension 106. However, in other examples, catheter 18
may be connected directly to IMD 12 by coupling 42, or coupling 42 may
connect catheter extension 106 to IMD 12, which, in turn, connects
catheter 18 to the device. Regardless of the particular arrangement of
IMD, therapy delivery component, and coupling, measurement circuit 50 of
IMD 12 may be configured to identify catheter 18 based on a signal
generated as an output to an electrical input applied by the circuit
across coupling 42.

[0048] In the example of FIG. 3, coupling 42 includes first connector 46
connected to proximal end 18A of catheter 18. Coupling 42 also includes
second connector 48 connected to IMD 12, e.g., to internal tubing 38 as
shown in the example of FIG. 3. Second connector 48 of coupling 42 is
configured to receive first connector 46 and is connected to measurement
circuit 50 of IMD 12. For example, as illustrated in FIG. 3, second
connector 48 of coupling 42 may include a male connector configured to
receive female first connector 46 of the coupling. In another example,
second connector 48 connected to IMD 12 may include a female connector
configured to receive a male connector 46 connected to catheter 18. In
any event, some part or all of first connector 46 connected to end 18A of
catheter 18 and second connector 48 connected to IMD 12 may include an
electrically conductive material. For example, first connector 46 may
include conductor 46a and second connector 48 may include conductors 48a,
48b. Conductors 48a and 48b of second connector 48 are each independently
connected to measurement circuit 50. Conductors 46a and 48a, 48b for
first and second connectors 46, 48, respectively, may be formed of the
same or different electrically conductive material or materials. For
example, one or all of conductors 46a and 48a, 48b may be fabricated from
copper, steel, or another electrically conductive metal. In some
examples, one or both of conductors 46a and 48a may be fabricated from a
biocompatible electrically conductive material, including, e.g.,
titanium, stainless steel, platinum or gold. In any event, connecting
first connector 46 to second connector 48, and, in particular, connecting
conductor 46a to two conductors 48a, 48b may act to complete measurement
circuit 50 such that coupling a signal, e.g. voltage, current,
resistance, or capacitance, is generated when measurement circuit applies
an electrical input, e.g. a constant current or voltage, across coupling
42.

[0049] Different mechanical configurations of coupling 42, including first
connector 46 and second connector 48 are possible in examples according
to this disclosure. In one example, coupling 42 may be configured such
that a mechanical coupling between connectors 46 and 48 also serves to
close measurement circuit 50, e.g. via conductor 46a and conductors 48a,
48b. In such an example, the size, e.g. thickness, or other geometrical
characteristic, or the material of the mechanical coupling 42 may be
varied based on the type and configuration of catheter 18. In another
example, however, coupling 42 may include a separate electrical
connection for closing measurement circuit 50 from the mechanical
coupling that physically connects proximal end 18A of catheter 18 to IMD
12. In this example, the size or material of the electrical connection
that functions to close measurement circuit 50 when catheter 18 is
connected to IMD 12 by coupling 42 may be varied based on the type and
configuration of catheter 18. The mechanical or other coupling employed
in coupling 42 may be fabricated from a variety of materials, including
metals and plastics and may be incorporated into catheter 18 in a variety
of ways, including, e.g., embedding the coupling in the wall of proximal
end 18A of catheter 18. Various mechanical couplings may be employed in
coupling 42, including threaded couplings, snap or press fit couplings,
set screws, and the like.

[0050] Although the foregoing example includes identifying catheter 18
based on the physical properties of components contained completely
within coupling 42, e.g. conductor 46a, in other examples, the catheter,
or another therapy delivery component may be identified based on
properties of components that are outside of or extend beyond the
coupling between the catheter and IMD 12. For example, connecting IMD 12
and catheter 18 may complete measurement circuit 50 such that the circuit
applies an electrical input, e.g. a measurement current through coupling
42 and across some conductive element contained in the catheter beyond
the coupling, i.e. distal to the IMD and the coupling toward distal end
18B of the catheter.

[0051]FIG. 4A is a diagram illustrating an example of measurement circuit
50 of IMD 12 including battery 60, current source 62, voltmeter 64, and
coupling 42, which includes first connector 46 and second connector 48.
Measurement circuit 50 in FIG. 4A is intended for illustrative purposes
and thus some of the details of the physical configuration of coupling
42, including, e.g. conductors 46a and 48a, 48b of first and second
connectors 46, 48, respectively, have been omitted from the figure for
simplicity. However, joining first and second connectors 46 and 48,
respectively, of coupling 42 in FIG. 4A to complete measurement circuit
50 includes connecting conductor 46a to conductors 48a, 48b, as
illustrated in FIG. 3. In FIG. 4A, battery 60 acts as a power source for
measurement circuit 50. In one example, measurement circuit 50 may be
connected to battery 44 of IMD 12, instead of including an additional
separate power source. In any event, battery 60 supplies power to current
source 62, which drives measurement circuit 50 with a known measurement
current, I. Although FIG. 4A illustrates completing measurement circuit
by connecting first and second connectors 46, 48, respectively, such that
the circuit is connected to the positive and negative terminals of
battery 60, in another example, one side of the circuit may be connected
to a ground instead of the negative side of the battery or other power
source employed in measurement circuit 50. In the example of FIG. 4A,
connecting IMD 12 and catheter 18 via coupling 42 may act to complete
measurement circuit 50 such that current, I, from current source 62 may
flow across conductor 46, which includes a known resistance, RC.
Measurement circuit 50 also includes voltmeter 64. Voltmeter 64 may be
configured to produce an output voltage signal, VO, when current, I,
from current source 62 is applied across coupling 42, and, in particular,
across conductor 46 including resistance, RC.

[0052] Measurement circuit 50 may then identify catheter 18 connected to
IMD 12 based on the output voltage, VO. For example, measurement
circuit 50 may communicate output voltage, VO, from voltmeter 64 to
a processor as a digital voltage value, e.g. via an ADC. In another
example, an analog comparator or other circuit associated with
measurement circuit 50 may compare output voltage, VO, from
voltmeter 64 to a threshold voltage to generate an indication of the type
of catheter, and communicate the signal to the processor, e.g., via an
ADC. In one example, the processor and other digital components necessary
to identify catheter 18 based on the analog electrical output signals
generated by measurement circuit 50 may be included in the measurement
circuit. In another example, however, measurement circuit 50 may
communicate with, e.g., processor 26 and memory 28 in the process of
identifying the type and configuration of catheter 18. In one example,
processor 26 of IMD 12 cross-references the voltage, VO, from
voltmeter 64, e.g., in a look-up table or other organized aggregation of
data of therapy delivery components and associated voltages stored on
memory 28. In other words, in such an example, processor 26 identifies
the type and configuration of catheter 18 connected to IMD 12 directly
based on the output voltage, VO, measured by voltmeter 64, which may
have been previously mapped to different types of catheters with
different known resistances. In another example, measurement circuit 50
may communicate the output voltage signal, VO, from voltmeter 64 to
processor 26, which may identify the type and configuration of catheter
18 by calculating the resistance, RC, of conductor 46a of first
connector 46 from the voltage. For example, processor 26 may calculate
the resistance of conductor 46a of first connector 46 from the voltage,
VO, generated as an output to the input current, I, applied by
current source 62 of measurement circuit 50 across coupling 42 and search
for the resistance in a look-up table or other organized aggregation of
data of therapy delivery components and associated resistances stored on
memory 28 of the IMD 12, or memory of another device, e.g. programmer 20.

[0053] In one example, conductor 46a of first connector 46 connected to
end 18A of catheter 18 is formed from a titanium alloy including an
electrical resistivity of approximately 42×10-8 ohm meters
(Ωm) or 42 micro ohm meters (μΩm). Catheter 18 is
connected to IMD 12 via coupling 42 such that first connector 46, and, in
particular, conductor 46a of the first connector is connected to
conductor 48a of second connector 48, which completes measurement circuit
50 such that a voltage signal generated as an output to an input applied
by the measurement circuit across coupling 42. Measurement circuit 50
communicates the output voltage signal to, e.g., processor 26 of IMD 12,
or a processor of another device communicatively connected to the IMD,
e.g. programmer 20, which, in turn, calculates the resistance, e.g.
approximately 42 micro ohm meters (μΩm), of first connector 46
from the voltage signal generated by coupling 42. After calculating the
resistance of titanium conductor 46a of first connector 46 from the
voltage signal generated as an output to an input applied by measurement
circuit 50 across coupling 42, processor 26 identifies catheter 18 by
searching for the resistance in a look-up table of different types of
therapy delivery components and associated resistances stored on memory
28 of the IMD or another device, e.g. programmer 20. For example,
processor 26 identifies catheter 18 as a single lumen catheter with a
stock length of approximately 89.0 centimeters and an inner diameter of
approximately 0.053 centimeters. Processor 26 in conjunction with
measurement circuit 50 need not identify the type and configuration of
catheter 18, or, e.g. the connection status of the catheter, continually,
but may make such identifications or other determinations periodically,
e.g. in order to reduce the load on power source 44 of IMD 12 and thereby
potentially increase the longevity of the device.

[0054] In some examples, measurement circuit 50, alone or in conjunction
with other components, e.g. processor 26, or a processor of another
device, may identify characteristics of catheter 18 other than those
described above. In one example, measurement circuit may identify whether
or not catheter 18 is safe for use with other medical equipment,
including, e.g., a Magnetic Resonance Imaging (MRI) machine.

[0055] In addition to or in lieu of employing known resistances, some part
or all of first connector 46 connected to end 18A of catheter 18 may
include a known electrical capacitance. First connector 46 may include,
in addition to conductor 46a, a dielectric material such that connecting
first connector 46 and second connector 48 interposes the dielectric
material between conductor 46a of the first connector and conductor 48a
of the second connector. The dielectric material of first connector 46
may include a known capacitance. In such an example, connecting first
connector 46 to second connector 48 may act to complete measurement
circuit 50 such that a voltage signal is generated as an output to an
electrical input, e.g. constant current, applied by the circuit across
coupling 42. Measurement circuit 50, alone or in conjunction with, e.g.
processor 26 of IMD 12, or a processor of another device communicatively
connected to the IMD, e.g. programmer 20, may identify catheter 18 based
on the voltage signal or, in one example, may calculate the capacitance
of first connector 46, e.g. of the dielectric of the first connector from
the voltage signal generated by coupling 42. In the latter case, after
calculating the capacitance of first connector 46 from the voltage signal
generated as an output of measurement circuit 50, processor 26, for
example, may identify, e.g., the type and configuration of catheter 18
by, e.g., searching for the resistance in a look-up table or other
organized aggregation of different types of therapy delivery components
and associated resistances stored on memory 28 of IMD 12 or another
device, e.g. programmer 20.

[0056] FIGS. 4B and 4C are diagrams illustrating two examples of
measurement circuit 50 of IMD 12, in which some part or all of first
connector 46 connected to end 18A of catheter 18 includes a known
electrical capacitance. In order to employ capacitance as a means by
which the type and configuration of catheter 18 is identified, it may be
necessary to provide an alternating current (AC) source across coupling
42. As such, in the examples of FIGS. 4B and 4C two different mechanisms
are employed to effectively convert DC battery 60 to an AC source as an
electrical input across coupling 42.

[0057] The example of FIG. 4B illustrates measurement circuit 50 including
battery 60, DC to AC inverter 66, AC source 68, voltmeter 64, and
coupling 42, which includes first connector 46 and second connector 48.
In the example of FIG. 4B, direct current from battery 60 is converted to
alternating current via DC to AC inverter 66, thereby generating AC
source 68. AC source 68 provides an alternating current input across
coupling 42, which includes first connector 46 and second connector 48.
First connector 46 includes capacitor 70, which may include a dielectric
material, e.g. air, with a known capacitance. In such an example,
connecting IMD 12 and catheter 18 via coupling 42 may act to complete
measurement circuit 50 such that current from AC source 68 flows across
connector 46, which includes a known capacitance, CC. Measurement
circuit 50 also includes voltmeter 64. Voltmeter 64 may be configured to
produce an output voltage signal, VO, when current from AC source 68
is applied across coupling 42, and, in particular, across conductor 46
including capacitance, CC.

[0058] Measurement circuit 50 may then identify catheter 18 connected to
IMD 12 based on the output voltage, VO. For example, measurement
circuit 50 may communicate output voltage, VO, from voltmeter 64 to
a processor as a digital voltage value, e.g. via an ADC. In another
example, an analog comparator or other circuit associated with
measurement circuit 50 may compare output voltage, VO, from
voltmeter 64 to a threshold voltage to generate an indication of the type
of catheter, and communicate the signal to the processor, e.g., via an
ADC. In one example, the processor and other digital components necessary
to identify catheter 18 based on the analog electrical output signals
generated by measurement circuit 50 may be included in the measurement
circuit. In another example, however, measurement circuit 50 may
communicate with, e.g., processor 26 and memory 28 in the process of
identifying the type and configuration of catheter 18. In one example,
processor 26 of IMD 12 cross-references the voltage, VO, from
voltmeter 64, e.g., in a look-up table or other organized aggregation of
data of therapy delivery components and associated voltages stored on
memory 28. In other words, in such an example, processor 26 identifies
the type and configuration of catheter 18 connected to IMD 12 directly
based on the output voltage, VO, measured by voltmeter 64, which may
have been previously mapped to different types of catheters with
different known capacitances. In another example, measurement circuit 50
may communicate the output voltage signal, VO, from voltmeter 64 to
processor 26, which may identify the type and configuration of catheter
18 by calculating the capacitance, CC, of capacitor 70 of first
connector 46 from the voltage. For example, processor 26 may calculate
the capacitance, CC, of capacitor 70 of first connector 46 from the
voltage, VO, generated as an output to the input current applied by
AC source 68 of measurement circuit 50 across coupling 42 and search for
the capacitance in a look-up table or other organized aggregation of data
of therapy delivery components and associated capacitances stored on
memory 28 of the IMD 12, or memory of another device, e.g. programmer 20.

[0059] In the example of FIG. 4c, instead of employing DC to AC inverter
66 shown in FIG. 4B, measurement circuit 50 simulates an AC source by
toggling between positive and negative sides of DC battery 60 over time.
For example, in FIG. 4c, current IA of current source 72 may be applied
to coupling 42 with top switch 74 closed and bottom switch 76 open to
yield+VDC. At some period of time later, current IA of current
source 72 may be applied to coupling 42 with top switch 74 open and
bottom switch 76 closed to yield -VDC. In this manner, current IA
will simulate AC source fluctuating between +VDC and -VDC
applied across coupling 42. The example of measurement circuit 50
illustrated in FIG. 4c may function to identify the type and
configuration of catheter 18 based on the known capacitance, CC, of
capacitor 70 in a substantially similar manner to that described with
reference to the example of FIG. 4B.

[0060] Additional configurations of coupling 42 between catheter 18 and
IMD 12 are contemplated. For example, coupling 42 may include optical
transmitter and receiver components by which an optical signal is
generated and received between, e.g., first connector 46 and second
connector 48. Measurement circuit 50, alone or in conjunction with other
components, including, e.g., processor 26, or a processor of another
device, e.g. programmer 20, may identify catheter 18 by detecting the
wavelength of the optical signal transmitted and received by coupling 42
and searching for the wavelength in a look-up table of therapy delivery
components and associated resistances stored on memory 28 of IMD 12 or
another device, e.g. programmer 20.

[0061] In addition to identifying catheter 18, measurement circuit 50,
and, e.g., processor 26 of IMD 12, or a processor of another device may
also be configured to identify a connection status between the catheter
and IMD based on a signal generated as an output to an electrical input
applied by circuit 50 across coupling 42. During or after implantation,
catheter 18 may become partially or completely disconnected from IMD 12,
in which case, continuing to pump a therapeutic fluid from the device,
e.g. via pump 32 may act to deliver the fluid in unplanned dosages to
unintended sites with the body of patient 16. As such, it may be useful
to clinicians and patients to have awareness of the connection status
between catheter 18 and IMD 12. Because changes in the connection between
catheter 18 and IMD 12 may act to change the character and/or magnitude
of the signal generated by coupling 42, the signal may form a basis for
identifying the connection status in a manner similar to described above
for identifying catheter 18 based thereon.

[0062] In one example, some part or all of first connector 46 connected to
end 18A of catheter 18 may include a known electrical resistance. In such
an example, connecting first connector 46 to conductor second connector
48 may act to complete measurement circuit 50 such that a voltage signal
is generated as an output to an electrical input, e.g. constant current,
applied by the circuit across coupling 42. However, in the event that the
connection between first and second connectors 46, 48, respectively, is
compromised such that the catheter 18 becomes partially or completely
disconnected from IMD 12, the signal generated as an output in
measurement circuit 50 will change. In such examples, measurement circuit
50, alone or in conjunction with, e.g., processor 26 of IMD 12, or a
processor of another device communicatively connected to the IMD, e.g.
programmer 20, may be configured to compare the output voltage directly
to one or more thresholds indicative of a connection status between the
IMD and catheter 18 or calculate the resistance of first connector 46
from the voltage signal and compare the resistance to the threshold(s)
indicative of connection status between IMD and catheter. For example,
catheter 18 may become partially disconnected from IMD 12, which may act
to effectively reduce the resistance of first connector 46 of coupling
42. Processor 26 may calculate the resistance of first connector 46 from
a voltage signal generated as an output to a known measurement current
applied by measurement circuit 50 across coupling 42 and compare the
calculated resistance to a threshold resistance to determine that
catheter 18 is partially disconnected from IMD 12. In the event catheter
18 becomes completely disconnected from IMD 12 measurement circuit 50 may
be broken such that the circuit does not generate any voltage signal,
based upon which the circuit, alone or in conjunction with, e.g.,
processor 26 may identify the catheter as disconnected from the IMD.

[0063] In one example, measurement circuit 50, alone or in conjunction
with, e.g., processor 26 of IMD 12, or a processor of another device may
identify the connection status between catheter 18 and IMD 12 based on a
signal generated as an output to an input applied by the circuit across
coupling 42 as at least one of connected, disconnected, or partially
disconnected. In the event, the connection status between catheter 18 and
the IMD 12 is identified as one of disconnected or partially disconnected
, processor 26 or another component of the IMD may be configured to
generate an alert, including, e.g. an audible, tactile, or visual alert.
For example, the connection status between catheter 18 and IMD 12 may be
identified as partially disconnected and processor 26 may issue a sound
from the IMD, or from programmer 20 in communication with the IMD. In
another example, processor 26 may cause IMD 12 to vibrate within patient
16 to indicate the connection status between the IMD and catheter 18. In
another example, processor 26 may communicate with programmer 20 to cause
the programmer to display an alert on a display of the device that
indicates that connection status between IMD 12 and catheter 18 has been
identified as, e.g., partially disconnected.

[0064] Referring again to the example of FIG. 2, upon instruction from
processor 26, fluid delivery pump 32 may draw fluid from reservoir 34 and
pumps the fluid through internal tubing 38 to catheter 18 through which
the fluid is delivered to patient 16 to effect one or more of the
treatments described above, e.g., in accordance with a program stored on
memory 28. Internal tubing 38 is a segment of tubing or a series of
cavities within IMD 12 that run from reservoir 34, around or through
fluid delivery pump 32 to catheter access port 40 and catheter 18.

[0065] Fluid delivery pump 32 can be any mechanism that delivers a
therapeutic fluid in some metered or other desired flow dosage to the
therapy site within patient 16 from reservoir 30 via implanted catheter
18. In one example, fluid delivery pump 32 is a squeeze pump that
squeezes internal tubing 38 in a controlled manner, e.g., such as a
peristaltic pump, to progressively move fluid from reservoir 34 to the
distal end of catheter 18 and then into patient 16 according to
parameters specified by the therapy program stored on memory 28 and
executed by processor 26.

[0066] In various examples, fluid delivery pump 32 may be an axial pump, a
centrifugal pump, a pusher plate pump, a piston-driven pump, or other
means for moving fluid through internal tubing 38 and catheter 18. In one
example, fluid delivery pump 32 is an electromechanical pump that
delivers fluid by the application of pressure generated by a piston that
moves in the presence of a varying magnetic field and that is configured
to draw fluid from reservoir 34 and pump the fluid through internal
tubing 38 and catheter 18 to patient 16.

[0067] Periodically, fluid may need to be supplied percutaneously to
reservoir 34 because all of a therapeutic fluid has been or will be
delivered to patient 16, or because a clinician wishes to replace an
existing fluid with a different fluid or similar fluid with different
concentrations of therapeutic ingredients. Refill port 26 can therefore
comprise a self-sealing membrane to prevent loss of therapeutic fluid
delivered to reservoir 30 via refill port 26. For example, after a
percutaneous delivery system, e.g., a hypodermic needle, penetrates the
membrane of refill port 26, the membrane may seal shut when the needle is
removed from refill port 26.

[0068] In general, memory 28 stores program instructions and related data
that, when executed by processor 26, cause IMD 12 and processor 26 to
perform the functions attributed to them in this disclosure. For example,
memory 28 of IMD 12 may store instructions for execution by processor 26
including, e.g., therapy programs, tables of different types of therapy
delivery components and an associated measurable parameter by which each
component may be uniquely identified, and any other information regarding
therapy delivered to patient 16 and/or the operation of IMD 12. Memory 28
may include separate memories for storing instructions, patient
information, therapy parameters, therapy adjustment information, program
histories, and other categories of information such as any other data
that may benefit from separate physical memory modules. Therapy
adjustment information may include information relating to timing,
frequency, rates and amounts of patient boluses or other permitted
patient modifications to therapy.

[0069] At various times during the operation of IMD 12 to treat patient
16, communication to and from IMD 12 may be necessary to, e.g., change
therapy programs, adjust parameters within one or more programs,
configure or adjust a particular bolus, or to otherwise download
information to or from IMD 12. Processor 26 controls telemetry module 30
to wirelessly communicate between IMD 12 and other devices including,
e.g. programmer 20. Telemetry module 30 in IMD 12, as well as telemetry
modules in other devices described in this disclosure, such as programmer
20, can be configured to use RF communication techniques to wirelessly
send and receive information to and from other devices respectively
according to, e.g., the 802.11 or Bluetooth specification sets, infrared
(IR) communication according to the IRDA specification set, or other
standard or proprietary telemetry protocols. In addition, telemetry
module 30 may communicate with programmer 20 via proximal inductive
interaction between IMD 12 and the external programmer. Telemetry module
30 may send information to external programmer 20 on a continuous basis,
at periodic intervals, or upon request from the programmer.

[0070] Power source 44 delivers operating power to various components of
IMD 12. Power source 44 may include a small rechargeable or
non-rechargeable battery and a power generation circuit to produce the
operating power. In the case of a rechargeable battery, recharging may be
accomplished through proximal inductive interaction between an external
charger and an inductive charging coil within IMD 12. In some examples,
power requirements may be small enough to allow IMD 12 to utilize patient
motion and implement a kinetic energy-scavenging device to trickle charge
a rechargeable battery. In other examples, traditional batteries may be
used for a limited period of time. As another alternative, an external
inductive power supply may transcutaneously power IMD 12 as needed or
desired.

[0071]FIG. 5 is a functional block diagram illustrating an example of
various components of external programmer 20 for IMD 12. As shown in FIG.
5, external programmer 20 may include user interface 82, processor 84,
memory 86, telemetry module 88, and power source 90. A clinician or
patient 16 interacts with user interface 82 in order to manually change
the parameters of a therapy program, change therapy programs within a
group of programs, view therapy information, view historical or establish
new therapy programs, or otherwise communicate with IMD 12 or view or
edit programming information. Processor 84 controls user interface 82,
retrieves data from memory 86 and stores data within memory 86. Processor
84 also controls the transmission of data through telemetry module 88 to
IMD 12. The transmitted data may include therapy program information
specifying various therapeutic fluid delivery parameters. Memory 86 may
store, e.g., operational instructions for processor 84 and data related
to therapy for patient 16.

[0072] Programmer 20 may be a hand-held computing device that includes
user interface 82 that can be used to provide input to programmer 20. For
example, programmer 20 may include a display screen that presents
information to the user and a keypad, buttons, a peripheral pointing
device, touch screen, voice recognition, or another input mechanism that
allows the user to navigate though the user interface of programmer 20
and provide input. In other examples, rather than being a handheld
computing device or a dedicated computing device, programmer 20 may be a
larger workstation or a separate application within another
multi-function device.

[0073] When programmer 20 is configured for use by a clinician, user
interface 82 may be used to transmit initial programming information to
IMD 12 including hardware information for system 10, e.g. the type of
catheter 18, the position of catheter 18 within patient 16, a baseline
orientation of at least a portion of IMD 12 relative to a reference
point, and software information related to therapy delivery and operation
of IMD 12, e.g. therapy parameters of therapy programs stored within IMD
12 or within programmer 20, the type and amount, e.g., by volume of
therapeutic fluid(s) delivered by IMD 12 and any other information the
clinician desires to program into IMD 12. The clinician may use
programmer 20 during a programming session to define one or more therapy
programs by which IMD 12 delivers therapy to patient 16, in which case
patient 16 may provide feedback to the clinician during the programming
session as to efficacy of a program being evaluated or desired
modifications to the program. Programmer 20 may assist the clinician in
the creation/identification of therapy programs by providing a methodical
system of identifying potentially beneficial therapy parameters.

[0074] Programmer 20 may also be configured for use by patient 16. When
configured as a patient programmer, programmer 20 may have limited
functionality in order to prevent patient 16 from altering critical
functions or applications that may be detrimental to patient 16. In this
manner, programmer 20 may only allow patient 16 to adjust certain therapy
parameters or set an available range for a particular therapy parameter.
In some cases, a patient programmer may permit the patient to control IMD
12 to deliver a supplemental, patient bolus, if permitted by the
applicable therapy program administered by the IMD, e.g., if delivery of
a patient bolus would not violate a lockout interval or maximum dosage
limit. Programmer 20 may also provide an indication to patient 16 when
therapy is being delivered or when IMD 12 needs to be refilled or when
the power source within programmer 20 or IMD 12 need to be replaced or
recharged.

[0075] As described above, processor 84 of programmer 20 may be configured
to execute one or more of the functions ascribed to processor 26 of IMD
12 in the process of identifying the type and/or configuration of
catheter 18, as well as the connection status between the catheter and
the IMD. Processor 84 may act in conjunction with measurement circuit 50
of IMD 12, as well as, in some examples, other components of programmer
20 and/or IMD 12, including, e.g. processor 26 and memories 28 and 86 of
the IMD and programmer, respectively. For example, in the event that
first connector 46 includes a known resistance and connecting catheter 18
to IMD 12 generate a voltage signal as an output to an input current
applied by measurement circuit 50 across coupling 42, as described above,
the circuit may function in conjunction with processor 84 of programmer
20 such that the processor calculates the resistance of first connector
46 from the voltage signal. After calculating the resistance of first
connector 46 from the output voltage signal on measurement circuit 50,
processor 84 may identify, e.g., the type and configuration of catheter
18 by, e.g., searching for the resistance in a look-up table or other
organized aggregation of different types of therapy delivery components
and associated resistances stored on memory 86 of programmer 20 or
another device, e.g. memory 28 of IMD 12.

[0076] Telemetry module 88 allows the transfer of data to and from
programmer 20 and IMD 12, as well as other devices, e.g. according to the
RF communication techniques described above with reference to FIG. 2.
Telemetry module 88 may communicate automatically with IMD 12 at a
scheduled time or when the telemetry module detects the proximity of IMD
12. Alternatively, telemetry module 88 may communicate with IMD 12 when
signaled by a user through user interface 82. To support RF
communication, telemetry module 88 may include appropriate electronic
components, such as amplifiers, filters, mixers, encoders, decoders, and
the like. Programmer 20 may also communicate with another programmer or
computing device via a wired or wireless connection using any of a
variety of communication techniques, and/or via exchange of removable
media, including, e.g., magnetic or optical disks, or memory cards or
sticks including, e.g., non-volatile memory. Further, programmer 20 may
communicate with IMD 12 or another device via, e.g., a local area network
(LAN), wide area network (WAN), public switched telephone network (PSTN),
or cellular telephone network, or any other terrestrial or satellite
network appropriate for use with programmer 20 and IMD 12.

[0077] Power source 90 may be a rechargeable battery, such as a lithium
ion or nickel metal hydride battery. Other rechargeable or conventional
primary cell batteries may also be used. In some cases, external
programmer 20 may be used when coupled to an alternating current (AC)
outlet, i.e., AC line power, either directly or via an AC/DC adapter.

[0078] In some examples, external programmer 20 may be configured to
recharge IMD 12 in addition to programming IMD 12. Alternatively, a
recharging device may be capable of communication with IMD 12. Then, the
recharging device may be able to transfer programming information, data,
or any other information described herein to IMD 12. In this manner, the
recharging device may be able to act as an intermediary communication
device between external programmer 20 and IMD 12.

[0079]FIG. 6 is a flow chart illustrating an example method of
identifying a therapy delivery component connected to an IMD. The method
of FIG. 5 includes applying an electrical input across a coupling between
an IMD and a therapy delivery component (100), generating an electrical
signal as an output to the input applied across the coupling (102) and
identifying the therapy delivery component based on the output electrical
signal (104). The functions of the method of FIG. 6 are described as
executed by IMD 12, and in particular, measurement circuit 50, alone or
in conjunction with, e.g., processor 26 and memory 28 of IMD 12. However,
in other examples, one or more of these functions may be carried out by
and/or in conjunction with other devices including, e.g., external
programmer 20.

[0080] In one example, the method of FIG. 5 includes applying an
electrical input across a coupling between an IMD and a therapy delivery
component (100). For example, battery 60 of measurement circuit 50 may
supply power to constant current source 62, which drives measurement
circuit 50 with a known current, I. Connecting IMD 12 and catheter 18 via
coupling 42 may act to complete measurement circuit 50 such that current,
I, from current source 62 may flow across conductor 46, which includes a
known resistance, RC. Thus, current source 62 of measurement circuit
50 applies input constant current, I, across conductor 46 of coupling 42.

[0081] The method of FIG. 6 also includes generating a signal as an output
to the input applied across the coupling between an IMD and therapy
delivery component (102). As illustrated in the examples of FIGS. 2 and
3, catheter 18 may be connected to IMD 12 by coupling 42. In one example,
some part or all of coupling 42 may include a known electrical or other
characteristic, including, e.g., a known resistance. Connecting IMD 12
and catheter 18 via coupling 42 may act to complete measurement circuit
50 such that a voltage signal is generated as an output to the current
input applied by the measurement circuit across the coupling. For
example, voltmeter 64 of measurement circuit may be configured to produce
an output voltage signal, VO, when current, I, from current source
62 is applied across coupling 42, and, in particular, across conductor 46
including resistance, RC.

[0082] In addition to generating the output electrical signal (102), the
method of FIG. 6 may include identifying the catheter based on the output
electrical signal (104). In one example, measurement circuit 50 may
identify catheter 18 connected to IMD 12 based on the output voltage,
VO. For example, measurement circuit 50 may communicate output
voltage, VO, from voltmeter 64 to a processor, e.g. via an ADC. In
one example, the processor and other digital components necessary to
identify catheter 18 based on the analog electrical output signals
generated by measurement circuit 50 may be included in the measurement
circuit. In another example, however, measurement circuit 50 may
communicate with, e.g., processor 26 and memory 28 in the process of
identifying the type and configuration of catheter 18. In one example,
processor 26 of IMD 12 cross-references the voltage, VO, to the
resistance, RC, of conductor 46a of first connector 46 of coupling
42, e.g., in a look-up table or other organized aggregation of data of
therapy delivery components and associated resistances stored on memory
28.

[0083] In another example, measurement circuit 50 may communicate the
output voltage signal, VO, from voltmeter 64 to processor 26, which
may identify the type and configuration of catheter 18 by calculating the
resistance, RC, of conductor 46a of first connector 46 from the
voltage. For example, processor 26 may calculate the resistance of
conductor 46a of first connector 46 from the voltage, VO, generated
as an output to the input current, I, applied by current source 62 of
measurement circuit 50 across coupling 42 and search for the resistance
in a look-up table or other organized aggregation of data of therapy
delivery components and associated resistances stored on memory 28 of the
IMD 12, or memory of another device, e.g. programmer 20. In some
examples, measurement circuit 50, alone or in conjunction with other
components, e.g. processor 26, or a processor of another device, may
identify characteristics of catheter 18 other than those described above.
In one example, measurement circuit 50 may identify whether or not
catheter 18 is safe for use with other medical equipment, including,
e.g., a Magnetic Resonance Imaging (MRI) machine.

[0084] In some examples, the method of FIG. 6 may also include identifying
a connection status between the IMD and therapy delivery component based
on the signal generated at the connection. For example, the method of
FIG. 6 may include identifying a connection status between catheter 18
and IMD 12 based on a signal generated as an output to an electrical
input applied by measurement circuit 50 across coupling 42. The
connection status between IMD 12 and catheter 18 may be identified as,
e.g., one of connected, disconnected, or partially disconnected. In one
example, coupling 42 may include a known electrical resistance. In such
an example, connecting catheter 18 to IMD 12 via coupling 42 may act to
complete measurement circuit 50 such that a voltage signal is generated
as an output to an input, e.g. current input applied across coupling 42
by the measurement circuit. However, in the event that the connection at
coupling 42 is compromised such that the catheter 18 becomes partially or
completely disconnected from IMD 12, the output voltage signal generated
by measurement circuit 50 will change.

[0085] In such examples, measurement circuit 50, alone or in conjunction
with, e.g., processor 26 of IMD 12, or a processor of another device
communicatively connected to the IMD, e.g. programmer 20, may be
configured to compare the output voltage directly to one or more
thresholds indicative of a connection status between the IMD and catheter
18 or calculate the resistance of first connector 46 from the voltage
signal and compare the resistance to the threshold(s) indicative of
connection status between IMD and catheter. For example, catheter 18 may
become partially disconnected from IMD 12, which may act to effectively
reduce the resistance of first connector 46 of coupling 42. Processor 26
may calculate the resistance of first connector 46 from a voltage signal
generated as an output to a constant current applied by measurement
circuit 50 across coupling 42 and compare the calculated resistance to a
threshold resistance to determine that catheter 18 is partially
disconnected from IMD 12. In the event catheter 18 becomes completely
disconnected from IMD 12 measurement circuit 50 may be broken such that
the circuit does not generate any voltage signal, based upon which the
circuit, alone or in conjunction with, e.g., processor 26 may identify
the catheter as disconnected from the IMD.

[0086] The method of FIG. 6 may also include generating an alert if the
connection status between IMD 12 and catheter 18 is identified as one of
disconnected or partially disconnected. In one example, measurement
circuit 50, alone or in conjunction with, e.g., processor 26 of IMD 12,
or a processor of another device may identify the connection status
between catheter 18 and IMD 12 based on a signal generated as an output
to an input applied by the circuit across coupling 42 as at least one of
connected, disconnected, or partially disconnected. In the event, the
connection status between catheter 18 and the IMD 12 is identified as one
of disconnected, or partially disconnected, processor 26 or another
component of the IMD may be configured to generate an alert, including,
e.g. an audible, tactile, or visual alert. For example, the connection
status between catheter 18 and IMD 12 may be identified as partially
disconnected and processor 26 may issue a sound from the IMD, or from
programmer 20 in communication with the IMD. In another example,
processor 26 may cause IMD 12 to vibrate within patient 16 to indicate
the connection status between the IMD and catheter 18. In another
example, processor 26 may communicate with programmer 20 to cause the
programmer to display an alert on a display of the device that indicates
that connection status between IMD 12 and catheter 18 has been identified
as, e.g., partially disconnected.

[0087] Although the foregoing examples are described with reference to a
fluid delivery device connected to a catheter and configured to deliver a
therapeutic fluid to a patient, the techniques for identifying therapy
delivery components disclosed are equally applicable to other types of
medical devices. For example, the disclosed techniques may be employed to
identify medical leads, including, e.g., electrical stimulation leads
connected to an implantable pulse generator (IPG) configured to deliver
electrical stimulation to a patient via electrodes connected to the lead.
The IPG and lead may be configured to deliver neurostimulation, e.g.
spinal cord stimulation (SCS), peripheral nerve field stimulation (PNFS),
peripheral nerve stimulation (PNS), deep brain stimulation (DBS), cardiac
stimulation, occipital nerve stimulation (OCS), and other types of
electrical stimulation.

[0089] In the example of FIG. 7, lead 162 is connected to IPG 150 by
coupling 166 that has a known physical property, e.g. electrical
resistance or capacitance, based upon which the type and particular
configuration of the therapy delivery component may be identified. In one
example, coupling 166 between lead 162 and IPG 150 may include a first
connector connected to a proximal end of the lead, i.e. an end closest to
the IPG. Some part or all of the first connector of coupling 166
connected to lead 162 may include a known electrical resistance. Coupling
166 may also include a second connector connected to IPG 150 and
measurement circuit 168 of the IPG. The second connector of coupling 166
may be configured to receive the first connector connected to lead 162.
In such an example, connecting the first connector connected to lead 162
with the second connector connected to IPG 150 may act to complete
measurement circuit 168 such that a voltage signal is generated as an
output to an electrical input, e.g. current input applied by the
measurement circuit across coupling 166. Measurement circuit 168, alone
or in conjunction with other components, e.g., processor 154 may then
identify lead 162 directly based on the output voltage or by calculating
the resistance of the first connector of coupling 166 from the voltage.
For example, measurement circuit 168 may generate the output voltage and
transmit the voltage to processor 154, e.g. via an ADC. Processor 154 may
then, e.g., calculate the resistance of the first connector from the
voltage output by measurement circuit 168 and search for the resistance
in a look-up table or other organized aggregation of data of therapy
delivery components and associated resistances stored on memory 156.

[0090] In other examples, the first connector of coupling 166 between lead
162 and IPG 150 may include a known capacitance instead of resistance, by
which, in a similar fashion as described in the foregoing example, the
type and particular configuration of the lead connected to the IPG may be
identified. Additional configurations of the coupling between a medical
and an IPG are also possible, including, e.g. a coupling including
optical components configured to generate optical signals that may be
employed to identify a lead connected to an IPG.

[0091] Because lead 162 conducts electricity to electrodes 164 in the
example IPG 150 of FIG. 7, coupling 166 may need to be designed such that
it does not to modify the electrode-conductor impedances of the lead,
because electrical stimulation is delivered by therapy delivery module
152 to patient 16 via those paths. As such, coupling 166 may require
conductive elements separate from the elements conducting electricity
between IPG 150, lead 162, and electrodes 164. FIG. 8 is a conceptual
diagram illustrating an example configuration of the manner in which
coupling 166 may connect lead 162 to IPG 150 without disturbing or
modifying the electrical connections conducting electricity between IPG
150, lead 162, and electrodes 164. In FIG. 8, lead 162 includes lead body
180, conductors 182, and ring contacts 184. Conductors 182 run the length
of lead 162 and are electrically coupled toward the distal end of the
lead to respective ones of electrodes 164 (not shown). At the proximal
end of lead 162, each conductor 182 is connected to a respective ring
contact 182. The proximal end of lead 162 is received by IPG 150 such
that each of ring contacts 184 couple with corresponding electrical
contacts on the IPG, thereby connecting electrodes 164 to therapy
delivery module 152.

[0092] In the example of FIG. 8, coupling 166 connects the proximal end of
lead 162 to IPG 150 via an electrical connection that is separate from
the connection between electrodes 164 and therapy delivery module 152,
i.e. conductors 182 and ring contacts 184. Coupling 166 may include an
electrical contact on lead 162 that engages a contact on IPG 150 such
that connecting lead 162 to IPG 150 functions to complete measurement
circuit 168, which may, in turn, cause a voltage signal to be generated
as an output to an electrical input, e.g. current input applied by the
measurement circuit across coupling 166. Other physical examples of
coupling 166 are contemplated by this disclosure. For example, coupling
166 may be located somewhere other than the proximal end of lead 162, as
shown in the example of FIG. 8.

[0093] Although the target therapy delivery site described with reference
to the foregoing examples is proximate to the spinal cord of a patient,
other applications of therapy systems in accordance with this disclosure
include alternative delivery sites. In some examples, the target delivery
site may be proximate to different types of tissues including, e.g.,
nerves, e.g. sacral, pudendal or perineal nerves, organs, muscles or
muscle groups. In one example, a catheter may be positioned to deliver a
therapeutic fluid to a deep brain site or within the heart or blood
vessels. Delivery of a therapeutic fluid within the brain may help manage
a number of disorders or diseases including, e.g., chronic pain,
diabetes, depression or other mood disorders, dementia,
obsessive-compulsive disorder, migraines, obesity, and movement
disorders, such as Parkinson's disease, spasticity, and epilepsy. A
catheter may also be positioned to deliver insulin to a patient with
diabetes. In other examples, the system may deliver a therapeutic fluid
to various sites within a patient to facilitate other therapies and to
manage other conditions including peripheral neuropathy or post-operative
pain mitigation, ilioinguinal nerve therapy, intercostal nerve therapy,
gastric drug induced stimulation for the treatment of gastric motility
disorders and/or obesity, and muscle stimulation, or for mitigation of
peripheral and localized pain e.g., leg pain or back pain.

[0094] The techniques described in this disclosure for identifying therapy
delivery components may be implemented, at least in part, in hardware,
software, firmware or any combination thereof. For example, various
aspects of the described techniques may be implemented within one or more
processors, including one or more microprocessors, digital signal
processors (DSPs), application specific integrated circuits (ASICs),
field programmable gate arrays (FPGAs), or any other equivalent
integrated or discrete logic circuitry, as well as any combinations of
such components. The term "processor" or "processing circuitry" may
generally refer to any of the foregoing logic circuitry, alone or in
combination with other logic circuitry, or any other equivalent
circuitry. A control unit comprising hardware may also perform one or
more of the techniques of this disclosure.

[0095] Such hardware, software, and firmware may be implemented within the
same device or within separate devices to support the various operations
and functions described in this disclosure. In addition, any of the
described units, modules or components may be implemented together or
separately as discrete but interoperable logic devices. Depiction of
different features as modules or units is intended to highlight different
functional aspects and does not necessarily imply that such modules or
units must be realized by separate hardware or software components.
Rather, functionality associated with one or more modules or units may be
performed by separate hardware or software components, or integrated
within common or separate hardware or software components.

[0096] The techniques described in this disclosure may also be embodied or
encoded in a computer-readable medium, such as a computer-readable
storage medium, containing instructions. Instructions embedded or encoded
in a computer-readable storage medium may cause a programmable processor,
or other processor, to perform the method, e.g., when the instructions
are executed. Computer readable storage media may include random access
memory (RAM), read only memory (ROM), programmable read only memory
(PROM), erasable programmable read only memory (EPROM), electronically
erasable programmable read only memory (EEPROM), flash memory, a hard
disk, a CD-ROM, a floppy disk, a cassette, magnetic media, optical media,
or other computer readable media.

[0097] Various examples have been described. These and other examples are
within the scope of the following claims.